The present invention is directed generally to systems for gravel packing of wells, and more particularly is directed to systems which facilitate the gravel packing of wells, and particularly circulating gravel packing of wells, through a tubing string.
It is well known in the oil and gas industry to gravel pack wells penetrating unconsolidated earth formations to prevent disadvantageous deterioration or collapse of the formation proximate the wellbore. Circulating gravel packing includes the placing of a slurry containing the gravel into the well to a location proximate the formation, with the slurry fluid being returned through a screen to the surface, leaving the solids proximate the formation.
Conventional gravel pack tools are designed to be lowered through the casing, typically on the end of a tubing string. Conventional gravel pack tools are substantially larger than the tubing string. The problem, therefore, with conventional apparatus involves their use in existing wells, where tubing is already in place. Where it is determined that gravel packing of a well would assist in obtaining or maintaining production, conventional available techniques would have required either the removal of the existing tubing string from the well to facilitate introduction of conventional gravel pack tools into the well; or the pumping of a gravel slurry in a gel carrier through the tubing string. The pulling of the existing tubing string is a relatively expensive operation which in most cases will not be practical for work over wells. At the same time, however, the pumping of a gel-carried gravel slurry will typically not yield the same benefits of formation control as would be obtained with a circulating gravel pack, due to factors such as the difficulty in placing the slurry completely across an interval, etc.
Accordingly, the present invention provides a new method and apparatus for performing a circulating gravel pack through the tubing string, thereby facilitating the gravel packing of wells in a manner not obtainable with prior art methods and apparatus.